One possible reason could be that Peter is keeping secrets from MJ about his Spider - Man identity. In many versions, his secrecy creates misunderstandings and MJ might feel left out or betrayed, leading to her crying.
Another common theme is heroism. Since Peter B. Parker is a superhero, the fanfiction may show how MJ supports him in his heroic deeds, or how his superhero life affects their relationship. For example, he might have to choose between saving the city and being there for MJ at an important moment.
Love and support is a very common theme. MJ is often shown as a pillar of strength for Peter, and he in turn gives her a sense of adventure. For example, in many fanfics, MJ stands by Peter during his tough times as Spider - Man, whether it's dealing with a powerful villain or his own self - doubts.
In a fanfiction, MJ and Peter Parker could have an adventure that's separate from the main plot of Far From Home. For example, they could get lost in a small European town and have to rely on each other's skills to find their way back. MJ uses her intelligence to decipher clues, while Peter uses his Spidey - sense to avoid danger.
Another great one is 'Love in the Shadows'. This fanfic shows a more angsty side of their relationship. MJ is constantly worried about Peter's safety when he goes out to fight crime. It also explores how their relationship evolves over time, with some really well - written dialogue that captures the essence of their characters.
One great piece of Peter B. Parker and MJ fanfiction is 'A New Beginning'. It explores their relationship in an alternate universe where they face new challenges together. The story really dives deep into their characters and how they support each other.
It could end with Peter realizing his mistake and apologizing sincerely to MJ. He might open up about everything and they reconcile, with MJ forgiving him.